Article of footwear having midsole with support pillars and method of manufacturing same

ABSTRACT

An article of footwear includes an upper, a sole assembly, and a support assembly positioned in the sole assembly and including a plurality of pillars. Each pillar includes an outer layer and an inner layer of cushioning material contained with the outer layer.

FIELD OF THE INVENTION

This invention relates generally to an article of footwear, and, inparticular, to an article of footwear having a midsole with supportpillars positioned therein and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

A conventional article of athletic footwear includes two primaryelements, an upper and a sole structure. The upper provides a coveringfor the foot that securely receives and positions the foot with respectto the sole structure. In addition, the upper may have a configurationthat protects the foot and provides ventilation, thereby cooling thefoot and removing perspiration. The sole structure is secured to a lowerportion of the upper and is generally positioned between the foot andthe ground. In addition to attenuating ground reaction forces (i.e.,imparting cushioning), the sole structure may provide traction andcontrol foot motions, such as pronation. Accordingly, the upper and thesole structure operate cooperatively to provide a comfortable structurethat is suited for a variety of ambulatory activities, such as walkingand running.

The sole structure of athletic footwear generally exhibits a layeredconfiguration that includes a comfort-enhancing insole, a resilientmidsole formed from a polymer foam material, and a ground-contactingoutsole that provides both abrasion-resistance and traction. The midsoleis the primary sole structure element that imparts cushioning andcontrols foot motions. Suitable polymer foam materials for the midsoleinclude ethylvinylacetate or polyurethane that compress resilientlyunder an applied load to attenuate ground reaction forces. Conventionalpolymer foam materials are resiliently compressible, in part, due to theinclusion of a plurality of open or closed cells that define an innervolume substantially displaced by gas. The polymer foam materials of themidsole may also absorb energy when compressed during ambulatoryactivities.

It would be desirable to provide an article of footwear that reduces orovercomes some or all of the difficulties inherent in prior knowndevices. Particular objects and advantages will be apparent to thoseskilled in the art, that is, those who are knowledgeable or experiencedin this field of technology, in view of the following disclosure of theinvention and detailed description of certain embodiments.

SUMMARY

The principles of the invention may be used to advantage to provide anarticle of footwear with support pillars. In accordance with a firstaspect, an article of footwear includes an upper, a sole assembly, and asupport assembly positioned in the sole assembly and including aplurality of pillars. Each pillar includes an outer layer and an innerlayer of cushioning material contained with the outer layer.

In accordance with another aspect, an article of footwear includes anupper, a sole assembly, and a support assembly positioned in a heelportion of the sole assembly and including a plurality of pillars. Eachpillar includes an outer layer having an upper portion including a firstrecess formed of walls and a bottom. A lower portion has a second recessformed of walls and a top, with the bottom of the first recess and thetop of the second recess being in abutting relationship. An apertureextends through the bottom of the first recess and the top of the secondrecess. An inner layer of cushioning material is contained with theouter layer and extends through the aperture.

In accordance with a further aspect, a method of manufacturing anarticle of footwear includes the steps of forming a fluid-filled baghaving a plurality of apertures extending there through with a firstmold; inserting the fluid-filled bag into a second mold; pouring acushioning material into the second mold to form a support assembly withcushioning material covering the bag and extending through the aperturesof the fluid-filled bag to form pillars; removing the support assemblyfrom the second mold; cutting away a portion of the cushioning materialabout a periphery of the support assembly; cutting away a portion of aperiphery of the fluid-filled bag to expose the pillars formed therein;and securing the support assembly between an upper and an outsole toform an article of footwear.

In accordance with yet another aspect, an article of footwear formed bythe steps of forming a fluid-filled bag in a first mold and including aplurality of first recesses on a first side thereof and having a bottom,a plurality of second recesses on a second side thereof and having a topwith a plurality of apertures extending there through, with eachaperture extending through the bottom of a first recess and a top of asecond recess; inserting the fluid-filled bag into a second mold;pouring a cushioning material into the second mold to form a supportassembly with cushioning material covering the bag and extending intothe recesses and through the apertures of the fluid-filled bag to formpillars; removing the support assembly from the second mold; cuttingaway a portion of the cushioning material about a periphery of thesupport assembly; cutting away a portion of a periphery of thefluid-filled bag to expose the pillars formed therein; and securing thesupport assembly between an upper and an outsole to form an article offootwear.

Substantial advantage is achieved by providing an article of footwearwith support pillars. In particular, certain embodiments of the articleof footwear with support pillars can provide increased support, comfortand performance.

These and additional features and advantages disclosed here will befurther understood from the following detailed disclosure of certainembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an article of footwear.

FIG. 2 is a perspective view of a mold used to form a fluid-filled bagused in the formation of a support assembly of the article of footwearof FIG. 1.

FIGS. 3A-C are elevation views of the use of the mold of FIG. 2 to formthe fluid-filled bag used in the formation of the support assembly ofthe article of footwear of FIG. 1.

FIG. 4 is a perspective view of the fluid-filled bag formed in the moldof FIG. 2.

FIG. 5 is a perspective view of a mold used to form the support assemblyof the article of footwear of FIG. 1.

FIG. 6 is a perspective view of the support assembly formed in the moldof FIG. 5, shown being trimmed to its final form.

FIG. 7 is a perspective view of the support assembly formed in the moldof FIG. 5, shown in its final form.

FIG. 8 is a section view of a portion of a pillar of the supportassembly of FIG. 7.

FIG. 9 is a section view of a portion of a pillar of another embodimentof the support assembly of FIG. 7.

FIG. 10 is a perspective view of another embodiment of the fluid-filledbag formed in the mold of FIG. 2.

The figures referred to above are not drawn necessarily to scale andshould be understood to provide a representation of the invention,illustrative of the principles involved. Some features of the article offootwear depicted in the drawings have been enlarged or distortedrelative to others to facilitate explanation and understanding. The samereference numbers are used in the drawings for similar or identicalcomponents and features shown in various alternative embodiments.Articles of footwear as disclosed herein would have configurations andcomponents determined, in part, by the intended application andenvironment in which they are used.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

The present invention may be embodied in various forms. A preferredembodiment of an article of footwear 10 is shown in FIG. 1. Footwear 10includes an upper 12 and a sole assembly 14 secured to upper 12. Soleassembly 14 may be secured to upper 12 by adhesive or any other suitablemeans. Footwear 10 has a medial, or inner, side 13 and a lateral, orouter, side 15. For purposes of general reference, footwear 10 may bedivided into three general portions: a forefoot portion 16, a midfootportion 18, and a heel portion 20. Portions 16, 18, and 20 are notintended to demarcate precise areas of footwear 10. Rather, portions 16,18, and 20 are intended to represent general areas of footwear 10 thatprovide a frame of reference during the following discussion.

Unless otherwise stated, or otherwise clear from the context below,directional terms used herein, such as rearwardly, forwardly, top,bottom, inwardly, downwardly, upwardly, etc., refer to directionsrelative to footwear 10 itself. Footwear 10 is shown in FIG. 1 to bedisposed substantially horizontally, as it would be positioned on ahorizontal surface when worn by a wearer. However, it is to beappreciated that footwear 10 need not be limited to such an orientation.Thus, in the illustrated embodiment of FIG. 1, rearwardly is toward heelportion 20, that is, to the left as seen in FIG. 1. Naturally, forwardlyis toward forefoot portion 16, that is, to the right as seen in FIG. 1,and downwardly is toward the bottom of the page as seen in FIG. 1. Toprefers to elements toward the top of the page as seen in FIG. 1, whilebottom refers to elements toward the bottom of the page as seen inFIG. 1. Inwardly is toward the center of footwear 10, and outwardly istoward the outer peripheral edge of footwear 10.

Sole assembly 14, which is generally disposed between the foot of thewearer and the ground, provides attenuation of ground reaction forces(i.e., imparting cushioning), traction, and may control foot motions,such as pronation. As with conventional articles of footwear, soleassembly 14 may include an insole (not shown) located within upper 12, amidsole 22, and an outsole 24. Midsole 22 is attached to upper 12 andfunctions as the primary shock-attenuating and energy-absorbingcomponent of footwear 10. Midsole 22 may be secured to upper 12 byadhesive or other suitable means. Suitable materials for midsole 22include polymer foam materials such as ethylvinylacetate orpolyurethane, or any other material that compresses resiliently. Outsole24 is attached to the lower surface of midsole 22 by adhesive or othersuitable means. Suitable materials for outsole 24 include polymers,e.g., polyether-block co-polyamide polymers (sold as Pebax® by ATOFINAChemicals of Philadelphia, Pa.), and nylon resins such as Zytel®, soldby Dupont. Other suitable materials for outsole 24 will become readilyapparent to those skilled in the art, given the benefit of thisdisclosure. In certain embodiments, sole assembly 14 may not include anoutsole layer separate from midsole 22 but, rather, the outsole maycomprise a bottom surface of midsole 22 that provides the externaltraction surface of sole assembly 14.

Sole assembly 14 includes a support assembly 26, which includes aplurality of pillars 25, described in greater detail below. As shown inthe embodiments illustrated herein, support assembly 26 is positioned inheel portion 20 of footwear 10. It is to be appreciated that supportassembly 26 can be positioned in one or more of heel portion 20, midfootportion 18 and/or forefoot portion 16. As illustrated here, supportassembly 26 is configured to span across footwear 10. However, it is tobe appreciated that support assembly 26 could be configured to bepositioned only on lateral side 15 or only on medial side 13 of footwear10. In other embodiments, support assembly 26 could have one portionextending across footwear 10 with another portion positioned in onlylateral side 15 or medial side 13. Other configurations of supportassembly 26 will become readily apparent to those skilled in the art,given the benefit of this disclosure.

The formation of a fluid-filled bag 27 (seen in FIG. 4) for use informing support assembly 26 is shown in FIGS. 2-4. A first mold 30, usedto form fluid-filled bag 27 is seen in FIG. 2. First mold 30 includes afirst portion 32 having a first recess 34 formed therein. A plurality offirst projections 36 extend outwardly from the bottom 38 of first recess34. A post 40 extends outwardly from each first projection 36. A firstchannel 41 extends between first recess 34 and an exterior of firstportion 32.

A second portion 42 of first mold 30 is joined to first portion 32 by ahinge 43 and includes a second recess 44 formed therein. A plurality ofsecond projections 46 extend outwardly from a bottom 48 of second recess44. Each second projection 46 includes an aperture 50 that receives acorresponding post 40 of first portion 32 when first mold 30 is closed.A second channel 51 extends between second recess 44 and an exterior ofsecond portion 42. Second channel 51 mates with first channel 41 offirst portion 32 when first mold 30 is closed, providing an input port,as described in greater detail below. First projections 36 and secondprojections 46 combine to define first and second recesses 66, 72,respectively, of fluid-filled bag 27, as described in greater detailbelow.

First mold 30 is used to form fluid-filled bag 27 as seen in FIGS. 3A-C.An injector 52 outputs a substantially tubular sheet of material 54downwardly in the direction of Arrow A from an aperture 56 formedtherein. First mold 30 is then closed about sheet of material 54. Aneedle 58 is then inserted into an input port 53 (formed by the matingof first channel 41 and second channel 51 of first mold 30) in thedirection of Arrow B and injects a fluid, such as air, into first mold30, forcing material 54 against the inner surfaces of first mold 30 toform fluid-filled bag 27 (seen in FIG. 4). In certain embodiments, avacuum may be applied to the exterior of sheet of material 54 withinfirst mold 30.

Material 54 used to form fluid-filled bag 27 may be thermoplasticpolyurethane (TPU), polyurethane, polyester, polyester polyurethane,polyether polyurethane, ethyl vinyl alcohol copolymers (EVOH) or scrapmaterial. Other suitable materials for use in forming fluid-filled bag27 will become readily apparent to those skilled in the art, given thebenefit of this disclosure.

As seen in FIG. 4, fluid-filled bag 27 is formed of an upper portion 60and a lower portion 62 joined by a parting line 64 created during themolding process by the junction of first portion 32 and second portion42 of first mold 30. Upper portion 60 includes a plurality of firstrecesses 66 having one or more walls 68 and a bottom 70. Walls 68 offirst recesses 66 may taper inwardly toward bottom 70. First recesses 66are formed by first projections 36 of first portion 32 of first mold 30.

Lower portion 62 similarly has a plurality of second recesses 72 havingone or more walls 74 and a top 76, which is in abutting relationshipwith bottom 70 of a corresponding first recess 66. Walls 74 of secondrecesses 72 may taper inwardly toward top 76. Second recesses 72 areformed by second projections 46 of second portion 42 of first mold 30.During the molding process described above with respect to FIGS. 3A-C, abottom 70 of a first recess 66 and a top 76 of a corresponding secondrecess 72 are sealed with one another as first projections 36 and secondprojections 46 sandwich sheet of material 54 therebetween. An aperture78 may extend through bottom 70 of a first recess 66 and thecorresponding top 76 of a second recess 72. Apertures 78 are formed byprojections 40 of first portion 32 of first mold 30.

In the embodiment illustrated, each first and second recess 66, 72 has asubstantially triangular shape and, therefore, includes three walls 68,74, respectively. Consequently, first and second projections 36, 46 havesubstantially triangular shapes as well. It is to be appreciated thatother shapes for first and second recesses 66, 72 are considered to bewithin the scope of the present invention, and that the number andconfiguration of the walls for first and second recesses 66, 72 willvary accordingly. Thus, for example, first and second recesses 66, 72may have square or rectangular shapes, which would require four walls68, 74, respectively. In such an embodiment, first and secondprojections 36, 46 of first mold 30 will naturally have correspondingsquare or rectangular shapes. Other shapes and configurations for firstand second recesses 66, 72 and, naturally, first and second projections36, 46 will become readily apparent to those skilled in the art, giventhe benefit of this disclosure.

In other embodiments, fluid-filled bag 27 may be produced by the wellknown thermoforming process, in which a pair of polymer layers areheated and placed between a pair of mold portions. A vacuum on theexterior of the layers and/or pressure between the layers draws thelayers into contours of the mold. The peripheries of the layers are thenpressed together to form a peripheral bond, and various interiorlocations may also be pressed together to form interior bonds, therebyforming fluid-filled bag 27.

In other embodiments, fluid-filled bag 27 may be manufactured by atwo-film technique, often referred to as twin-sheet bonding, wherein twoseparate layers of elastomeric film are formed to have the overall shapeof the bag. The layers are then welded together along their respectiveperipheries to form an upper surface, a lower surface, and sidewalls ofthe bag, and the layers are welded together at predetermined interiorlocations to impart a desired configuration to the bag. That is,interior portions of the layers are connected to form chambers of apredetermined shape and size at desired locations. The bag is thensubsequently pressurized above ambient pressure by inserting a nozzle orneedle, which is connected to a fluid pressure source, into a fill inletformed in the bag. After the bag is pressurized, the nozzle is removedand the fill inlet is sealed, by welding for example.

In other embodiments, fluid-filled bag 27 may be produced by the wellknown blowmolding process, in which a liquefied elastomeric material isplaced in a mold having the desired overall shape and configuration offluid-filled bag 27. Pressurized air is provided through an openingformed in the mold. The pressurized air forces the liquefied elastomericmaterial against the inner surfaces of the mold and causes the materialto harden in the mold, thereby forming the fluid-filled bag 27 havingthe desired configuration.

In certain embodiments, fluid-filled bag 27 may be colored to provide adesired aesthetic appearance. Fluid-filled bag 27 may be painted afterit has been formed in first mold 30, e.g., spray painted. The desiredcolor may be added by screen printing, sublimation or any other desiredmethod. In other embodiments, pigment may be added to material 54, whichis used to form fluid-filled bag 27, in order to provide a desiredcolor. Other methods of imparting color to fluid-filled bag 27 willbecome readily apparent to those skilled in the art, given the benefitof this disclosure. It is to be appreciated that fluid-filled bag 27 maybe painted a single color, or any combination of desired colors, and inany desired pattern to produce a desired aesthetic appearance.

A second mold 80, seen in FIG. 5, is used with fluid-filled bag 27 toform support assembly 26. Second mold 80 has a first portion 82 having arecess 84 formed therein. A first channel 86 extends from a periphery offirst portion 82 to recess 84. A second portion 88 has a projection 90formed thereon, with a second channel 92 extending from a periphery ofsecond portion 88 to projection 90. First portion 82 has a plurality ofpins 94 that are received in corresponding apertures 96 formed in secondportion 88 in order to register and align first portion 82 with secondportion 88.

Fluid-filled bag 27 is placed in recess 84 of first portion 82. Acushioning material 98, seen in FIGS. 6-8, is then poured into recess84, covering fluid-filled bag 27. Cushioning material 98 covers theexterior of fluid-filled bag 27, as well as filling first and secondrecesses 66, 72 and extending through apertures 78, thereby formingpillars 25, seen in FIGS. 6-8. Second portion 88 is then placed on firstportion 82 such that first and second channels 86, 92 are aligned withone another to define a channel that receives needle 58 used to formfluid-filled bag 27, a portion of projection 90 is received in recess84, and cushioning material 98 expands and fills first and secondrecesses 66, 72 and recess 84. Pillars 25 may have visible a partingline 102, formed at the junction of walls 68 and 74 of first recess 66and second recess 72, respectively, during the molding process.

A strip 104 of cushioning material 98 about the periphery of supportassembly 26 and the periphery 106 of fluid-filled bag 27 is then cutaway, exposing support assembly 26, as seen in FIGS. 6-7. Pillars 25 ofsupport assembly 26 can be seen to extend between the cushioningmaterial 98 that extends over the upper portion 60 of fluid-filled bag27 and the cushioning material 98 that extends beneath the lower portion62 of fluid-filled bag 27. Pillars 25, as seen in FIG. 8, are formed ofan outer layer 108, which comprises walls 68, 74 of first and secondrecesses 66, 72, respectively of fluid-filled bag 27, and an inner layer110 of cushioning material 98. Cushioning material 98 and, naturally,pillars 25, serve to act as a portion of midsole 22 of footwear 10.

In certain embodiments, cushioning material 98 is poured polyurethane.It is to be appreciated that other materials that will enhance thecushioning effect of support assembly 26 can be used for cushioningmaterial 98, such as ethyl vinyl acetate (EVA). Other suitable materialsfor cushioning material 98 will become readily apparent to those skilledin the art, given the benefit of this disclosure. In certainembodiments, cushioning material 98 could be pre-formed and merelyinserted into first and second recesses 66, 72 and around fluid-filledbag 27.

As seen in FIG. 8, pillars 25 may taper inwardly from their top toward amidpoint thereof, at parting line 102, and inwardly from a bottomthereof to the midpoint at parting line 102.

It is to be appreciated that cushioning material 98 may also be colored,and that different portions of cushioning material 98 may have differentcolors, thereby allowing one or more pillars 25 to have a first colorwith one or more other pillars 25 having a second different color. It isto be appreciated that any number of different colors can be used onpillars 25. Certain portions of pillars 25 may have one color with otherportions having different colors. Thus, outer layer 108 and inner layer110 of pillars 25 can have any desired color combination to provide adesired aesthetic design.

In addition, cushioning material 98 may not be uniform throughoutsupport assembly 26, that is, a first cushioning material 98 having afirst set of characteristics (density, compressibility, stiffness, etc.)could be initially poured into a first portion of second mold 80 and asecond cushioning material 98 that is different than the first (that is,it has a set of characteristics different than that of the firstcushioning material) could be poured into a second portion of secondmold 80. It is to be appreciated that any number of different cushioningmaterials can be provided throughout support assembly 26.

In another embodiment, as seen in FIG. 9, inserts 112 may be positionedwithin fluid-filled bag 27. As seen in this embodiment, inserts 112 arepositioned in first and second recesses 66, 72 and include a centralaperture 114 extending there through. Cushioning material 98 passesthrough apertures 114 and fills the interior of inserts 112, such thatinserts 112 are positioned within cushioning material 98 or inner layer110. Inserts 112 act to provide additional support for pillars 25. Incertain embodiments, inserts 112 may be formed of a material having agreater stiffness or rigidity than that of cushioning material 98. Forexample, inserts 112 may be formed of plastic.

It is to be appreciated that in certain embodiments, outer layer 108could be formed by injection molding material into a desired shape. Insuch an embodiment, the injection molded material is then placed intosecond mold 80 and cushioning material 98 is poured into the mold,forming pillars 25.

It is to be appreciated that in certain embodiments, as depicted in FIG.10, fluid-filled bag 27 may have first recesses 66 formed on only oneside thereof, with the other side of fluid-filled bag 27 beingsubstantially flat. Thus, cushioning material 98 extends into each firstrecess 66 such that the walls 68 of first recess 66 and cushioningmaterial 98 form outer layer 108 and inner layer 110, respectively, ofpillars 25.

It is to be appreciated that in certain embodiments, as seen in FIG. 10,fluid-filled bag 27 may include interior walls or partitions 114defining chambers 116. In such embodiments, only a portion of periphery106 of fluid-filled bag 27 may be cut away in the manner describedabove, thereby leaving intact some chambers 116 of fluid-filled bag 27.Chambers 116 may be at ambient pressure or inflated to a higherpressure. Chambers 116 can provide additional support for supportassembly 26.

By providing particular shapes, and sizes and locations of first andsecond recesses 66, 72, the support provided by pillars 25 can beoptimized. That is, the performance characteristics of footwear 10 canbe altered by positioning pillars 25 in desired locations and by formingpillars 25 with desired shapes. Accordingly, footwear 10 can beoptimized for particular activities, particular foot shapes or for anyother reason. Similarly, the amount and type of cushioning material 98can be varied throughout footwear 10 to optimize performance.

Similarly, by varying the thickness of the walls of fluid-filled bag 27,the thickness of outer layers 108 can be varied, thereby modifying theperformance of pillars 25.

In light of the foregoing disclosure of the invention and description ofvarious embodiments, those skilled in this area of technology willreadily understand that various modifications and adaptations can bemade without departing from the scope and spirit of the invention. Allsuch modifications and adaptations are intended to be covered by thefollowing claims.

1. An article of footwear comprising, in combination: an upper; a soleassembly; and a support assembly positioned in the sole assembly andincluding a plurality of pillars, each pillar comprising an outer layerand an inner layer of cushioning material contained within the outerlayer such that the entire outer layer completely circumferentiallysurrounds the inner layer without any voids between the inner layer andthe outer layer.
 2. The article of footwear of claim 1, wherein thesupport assembly is positioned in a heel portion of the sole assembly.3. The article of footwear of claim 1, wherein at least one of thepillars has a triangular cross-section.
 4. The article of footwear ofclaim 1, wherein the outer layer of the pillars is formed of an upperportion and a lower portion, the upper portion comprising a first recessformed of walls and a bottom, the lower portion comprised of a secondrecess formed of walls and a top, the bottom of the first recess and thetop of the second recess being in abutting relationship, an apertureextending through the bottom of the first recess and the top of thesecond recess, the inner cushioning material extending through theaperture.
 5. The article of footwear of claim 4, wherein the walls ofthe first recess taper inwardly to the bottom of the first recess, andthe walls of the second recess taper inwardly to the top of the secondrecess.
 6. The article of footwear of claim 1, wherein the outer layeris formed of TPU.
 7. The article of footwear of claim 1, wherein theinner cushioning material is formed of polyurethane.
 8. The article offootwear of claim 1, wherein the sole assembly includes a midsole, themidsole comprising the inner cushioning material contained within thepillars.
 9. The article of footwear of claim 1, wherein the pillarstaper inwardly from a top thereof to a midpoint thereof and from abottom thereof to the midpoint.
 10. The article of footwear of claim 1,wherein at least a portion of the support assembly has a desired color.11. The article of footwear of claim 1, wherein a first portion of thesupport assembly has a first color and a second portion of the supportassembly has a second color.
 12. The article of footwear of claim 11,wherein the first portion is the outer layer of a first pillar and thesecond portion is the outer layer of a second pillar.
 13. The article offootwear of claim 1, wherein a portion of the cushioning material has afirst color and a second portion of the cushioning material has a secondcolor.
 14. The article of footwear of claim 1, wherein the outer layerof the pillars is formed of an upper portion and a lower portion, theupper portion comprising a recess formed of walls and a bottom, theinner cushioning material extending into the recess.
 15. The article offootwear of claim 1, further comprising at least one insert positionedwithin the inner layer of a corresponding pillar.
 16. The article offootwear of claim 15, wherein the insert is formed of plastic.
 17. Thearticle of footwear of claim 1, wherein a first portion of the supportassembly has a first cushioning material and a second portion of thesupport assembly has a second cushioning material that is different thanthe first cushioning material.
 18. The article of footwear of claim 1,further comprising at least one interior chamber positioned within thesupport assembly.
 19. An article of footwear comprising, in combination:an upper; a sole assembly; and a support assembly positioned in a heelportion of the sole assembly and including a plurality of pillars, eachpillar comprising an outer layer comprising: an upper portion comprisinga first recess formed of walls and a bottom; and a lower portioncomprising a second recess formed of walls and a top, the bottom of thefirst recess and the top of the second recess being in abuttingrelationship; and an aperture extending through the bottom of the firstrecess and the top of the second recess; and an inner layer ofcushioning material contained within the outer layer and extendingthrough the aperture such that the outer layer completelycircumferentially surrounds the inner layer without any voids betweenthe inner layer and the outer layer.
 20. The article of footwear ofclaim 19, wherein the support assembly is positioned in a heel portionof the sole assembly.
 21. The article of footwear of claim 19, whereinat least one of the pillars has a triangular cross-section.
 22. Thearticle of footwear of claim 19, wherein the walls of the first recesstaper inwardly to the bottom of the first recess, and the walls of thesecond recess taper inwardly to the top of the second recess.
 23. Thearticle of footwear of claim 19, wherein the outer layer is formed ofTPU.
 24. The article of footwear of claim 19, wherein the innercushioning material is formed of polyurethane.
 25. The article offootwear of claim 19, wherein the sole assembly includes a midsole, themidsole comprising the inner cushioning material contained within thepillars.